It is a stiflingly hot day in Baton Rouge, Louisiana, and Andrea Riseborough wants to go for a walk.

A star in the ascendant, Riseborough is here making a new film, Oblivion, a science-fiction thriller in which she stars with Tom Cruise and Morgan Freeman.

Riseborough, who actually comes from Whitley Bay in North Tyneside, has spent a lot of time in America recently, so much so that she now prefers to live there – if she can be said to live anywhere, the past 12 months having been mostly spent living out of a suitcase.

She is only 30, but her career has followed a startlingly steep trajectory: from Rada to the RSC; from small but significant British films – Never Let Me Go, Made in Dagenham and Brighton Rock – to top-line name in big-budget Hollywood movies. Tom Cruise! Morgan Freeman!

But Riseborough, a woman of theatrical intensity who talks of her work in the tones of a religious calling, does not quite see it like that. 'Every time you get the chance to work with somebody you admire and would like to collaborate with… it feels like the best opportunity that’s ever come your way, whether that’s in fringe theatre or a really big-budget Hollywood movie.’

Baton Rouge is a sleepy southern city; at weekends, almost comatose. The restaurant where we have arranged to meet, away from the centre of town on a quiet street devoid of other businesses, is closed.

I am waiting outside in my taxi when Riseborough materialises at the window, as if from nowhere. She is wearing a blue summer dress, red trainers and a suede Stetson, and carrying a bottle of water.

I suggest we might find a cafe where we can talk. She suggests we go for a walk. It is 95 degrees. But Riseborough is someone who likes to 'absorb the place you’re in’, as she puts it, 'and see what the experience has to offer’; someone who prefers to ride the bus and 'absorb 20 people in a day’, rather than 'fly by in a car and really not see anybody’; somebody who would prefer to walk in the park rather than sit in a cafe.

'Perhaps,’ she says, 'there’s a bench where we can sit down.’

She directs the taxi to a park, where the driver deposits us at one end of a long lake. Riseborough says that she walks here often. We set off along the road. There is no pavement. There are large and expensive houses to our left; the lake is to our right. 'I have to be honest,’ she says after a while. 'I’m not sure that there is a bench.’

Riseborough is small, slight and pale. Her hair, which is naturally dark, is presently dyed a reddish colour for her new film, lending an almost transparent quality to her appearance. It is a curiosity that on screen she can look both very beautiful and quite plain, and all the gradations in between.

'I am quite odd-looking in real life,’ she says, in an accent that remains discernibly Geordie. 'My face is almost like a canvas – a blank canvas in the sense that the hair on my face is very, very fine and my skin is incredibly fair and my hair is quite dark, and that’s very unusual. It’s nice to surprise people with the way I really look. And it enables me to get the bus everywhere. Which I do.’

Riseborough’s latest role is playing an IRA terrorist, Collette, in James Marsh’s adaptation of the Tom Bradby thriller Shadow Dancer. As a young girl in Belfast, Collette has lost her brother in an exchange of gunfire between the IRA and British troops. Twenty years later, and now a single mother with a young son of her own, she has been sent to plant a bomb on the London Underground. When the bomb fails to go off, she is picked up by the security services and interrogated by an officer, Mac (Clive Owen), who presents her with an ultimatum: return to Belfast and work as an informer, betraying her own family, or go to jail and never see her son again.

Shadow Dancer is a taut, atmospheric and beautifully paced thriller, and Andrea Riseborough, who is in virtually every scene, gives an astonishing performance that has Oscar nomination written all over it.

We are walking on a road beside a lake in the broiling heat, conducting an interview. It’s most disconcerting, but Riseborough doesn’t seem to find it so. The houses really are beautiful – big mansions in the southern antebellum style, and passing them, Riseborough says, she has experienced that feeling that often comes upon travellers in a strange city of looking at a house and picturing herself living there.

'I do find I can see myself living in a lot of places,’ she says. 'Although there are so many places in the world that are in turmoil where I might not be as well equipped to live emotionally. But I don’t think any of us should rule anything out. Because if somebody’s got to survive there, we all should be able to, shouldn’t we?’

Riseborough has developed a particular approach to the peripatetic life. She carries nothing with her but for her clothes, her script and research material for the role she is playing. Wherever she goes, she says, she buys an instrument, a practice that began four years ago when she bought a banjo in a shop on Sunset Boulevard, and has since progressed to include a violin, a bass guitar, a banjolini and – this time – a red Destroyer guitar and a small Vox amp. 'If you’ve got three chords, you’ve got a real fighting chance you can do Dylan and Neil Young. And,’ she adds, 'I always buy the greatest works.’

The greatest works?

'Shakespeare. That perhaps is one of the things that makes me feel at home a little.’ She pauses. 'I have a lot of copies.’

Shakespeare was her first great, and most abiding, literary love, growing up in Newcastle; the bookish child who hung posters of Hieronymus Bosch paintings of Heaven and Hell on her bedroom wall and who was studying The Tempest when everyone else was out playing on their bikes. Her first Shakespearean role was playing Miranda when she was 14. 'I feel I have an awful lot to thank him for,’ she says. 'He opened me up to the possibility of all sorts of different worlds, [how] one mind might explore so many different lives.’

Her father, George, was a used-car salesman; her mother, Isabel, a secretary – the first generation in their families, as she puts it, 'to be middle class’. Her father’s mother was a cinema usherette, and he spent his childhood soaking up Hollywood classics – a love he passed on to Riseborough in their regular Sunday-afternoon excursions to the cinema. Her mother was in her 30s when she was taken by a friend to see Derek Jacobi playing Chekhov’s Ivanov at the Theatre Royal in Newcastle, 'and it completely blew her mind’. She went on to gain a Masters in Shakespearean and Jacobean studies from the Open University.

We have arrived at the far end of the lake. There is a bench! We sit down. The sun is beating down relentlessly. Riseborough swallows from her bottle of water. 'I think you’re going to get sunburn sitting here, Mick,’ she says. We set off for a nearby tree and sprawl in the shade.

I ask her about growing up in Newcastle, and she talks about the locals’ 'insatiable appetite for life’, and how 'everything is raw and unadulterated; the coastline is wild and the people are wild, in the best way’. There was enough money in the home to send Riseborough and her younger sister to private school. Her teachers told her she was good enough to get into Oxbridge. But to everybody’s consternation she left halfway through her A-levels.

'I just didn’t want to go to school any more,’ she says. 'Simple as that.’ She has no regrets. 'I gained a lot of books and I lost a lot of grammar. I gained a lot of books in the sense that I didn’t read any book to cram, so there was no [idea] of it just being a short-term suck it in and then regurgitate it.’ She pauses. 'Sometimes I can think of nothing more blissful than going to Berkeley and reading Byron for three years.’

She spent the next three years working in a number of jobs – making greetings cards, helping to run a Chinese restaurant – before finally applying to Rada. 'It was the right time for me.’ Riseborough has given different accounts of the moment at which she decided she wanted to be an actress. In one, she talked of a Pauline moment while shredding duck in the Chinese restaurant and feeling 'propelled’ to start taking acting seriously. In another, she talked of her ambition first being fired by seeing Marlon Brando in the film A Streetcar Named Desire.

'But really there was no one thing,’ she says now. 'It could just as much be the moment my sister was born as it could be Marlon Brando in A Streetcar Named Desire, and was probably more the moment my sister was born, because that is my life and those are the things that are most personal to me.’

Your sister being born inspired you to act?

She tries another tack. There comes a time, she says, when you realise that you can do something that may not be altogether enjoyable in itself – may, in fact, be physically and emotionally exhausting – but which affects and transports people. 'It’s that moment when Nureyev in The Prodigal Son flies eight feet in the air with one leg extended… nobody in the audience is anywhere other than where he is. It’s like being connected to something that all of us have. Humanity.’

Even before graduating from Rada she had landed three jobs on television. Her first theatrical lead role, in A Brief History of Helen of Troy at a fringe theatre in Soho, led to a stint at the National in 2006, where she was spotted by the director Sir Peter Hall. 'I remember David Suchet opening the door for me while I was being told simultaneously that Peter Hall wanted to cast me in Measure for Measure [playing Isabella] and to play [Strindberg’s] Miss Julie – and I was 25 at the time. And I almost couldn’t believe what was happening.’

Her performances won her the Ian Charleson Award for exceptional classical stage work from actors under 30, and led to Hall hailing her as 'one of the bravest and most impressive actresses I’ve come across in recent years’.

Perhaps Riseborough’s most extraordinary gift as an actress is her versatility – the ability to vanish in an astonishing variety of roles. It is hard to believe that it is the same actress inhabiting the vulnerable, naive waitress Rose in Brighton Rock; the young Margaret Thatcher in The Long Walk to Finchley; the sleek, determined Wallis Simpson in Madonna’s WE; and the spirited, sexually charged Angelica Fanshawe in the period television drama The Devil’s Whore, where she was called on to age from a virginal 17 to a careworn 40 – from royalist mistress to Leveller – and where her pale, jolie-laide looks called to mind a Bruegel painting. 'We were going for Van Dyck,’ she says.

She has a rare ability to convey emotion through silence, stillness, a single glance. She does a lot of work, she says, with facial muscles. 'Every character from head to toe uses different muscles. That’s something I really find enjoyable getting into.’

In Shadow Dancer her appearance is bleached and drawn, her dialogue pared to the bone – almost everything conveyed through the slightest nuances of expression. It is a brilliant portrayal of a character whose motives and feelings are concealed behind veils of ambiguity and uncertainty. Is Collette prepared to betray her family for the sake of her child and herself? Has she really bought the MI5 agent Mac’s promise of safety? Is she falling for him, as he is clearly falling for her?

Riseborough keeps you guessing right up to the film’s final twist in the tail. She likens immersing herself in the role to 'visiting a place you’ve never been before, and beginning to feel a kinship with that place and proud to know the secrets of it. I think there’s a great strength in secrecy – and that really is the key to Collette’s survival, her silence and her secrecy.

'I was a great fan of not speaking in the film. In fact, I would suggest on a regular basis that we would not speak, just because I felt her power was her silence. There is so much at stake for her that she couldn’t afford to be a chatty Cathy. But also it’s become who she is.’

'There is a huge burden on a person when they’re in virtually every scene,’ James Marsh, who is best-known for his award-winning documentaries Man on Wire and Project Nim, tells me. 'If Andrea doesn’t work, the film isn’t going to work. I’m not sure if she was aware of that or not, but I certainly was.’

Riseborough has a reputation for researching and preparing for her roles to an obsessive degree. For Collette, the screenwriter Tom Bradby introduced her to various people in Belfast who had been personally involved in the conflict.

'I think it was an important part of her preparation to understand what it would be like emotionally to be in that situation,’ Marsh says. 'There was someone she would call from time to time, just to make sure that what she was doing, and how we were doing it, passed a certain test.’

Riseborough says it was Mike Leigh, with whom she worked on Happy-Go-Lucky, who taught her one of her most valuable lessons as an actress: that building a character is not simply a matter of what you need to know – it is also what you need not to know. 'It’s very interesting to do a lot of research – sociologically, politically – but sometimes you have to stop yourself because too much knowledge can be unhelpful, and you’re expending a lot of energy trying to forget things. The thing is to focus really specifically and incredibly in-depth on whatever they do now, to the point where it becomes second nature and you don’t even think about it.’

Her portrayal of Margaret Thatcher in The Long Walk to Finchley, a light-hearted imagining of Mrs Thatcher’s struggle up the lower rungs of the ladder to power, brought the future prime minister unerringly to life – the forward tilt of her head, the determination in her stride – at the same time investing her with a decided friskiness absent from most accounts of the Iron Lady. 'One reason I found that piece so fascinating was that it was a version of the truth, but it wasn’t the truth,’ Riseborough says. 'It was a wonderfully fun romp through the early part of her life, which was actually full of turmoil and tragedy and misery and tenacity. I think the real Thatcher was unknowingly sexual. It became conscious once she realised it worked, but it was nurture not nature.’

Watching Meryl Streep portraying Mrs Thatcher in The Iron Lady – 'such a true, fearless, beautiful performance’, Riseborough breathes – was 'heartbreaking. It was like watching the end of what was once my own life.’ When she was doing the rounds promoting WE, she got to know Streep, who was promoting The Iron Lady at the same time, and they talked about the vagaries of portraying Mrs Thatcher, but Riseborough declines to discuss specifics. 'Things that really only somebody else who’d played the same character would understand, I suppose. So I’ll keep that one for us.’

She is similarly cryptic when I try to press her on working with Leigh, and his famous technique of preparation and improvisation. Riseborough is reported to have spent seven months preparing for her role in Happy-Go-Lucky as Sally Hawkins’s flatmate, Dawn, only to suffer a fate familiar to other actors who have worked with Leigh of seeing only a few minutes of her performance appear in the film. No actor who has worked with him, she says, would ever divulge Leigh’s process, 'because then it would be something that wasn’t precious, and nobody wants to ruin the gift he gave us. It’s very important that it remains secretive in that way. I know that people sometimes have a funny reaction to that. But what a great gift to give to an artist, to allow them to live… as somebody else.’

At such times talking with Riseborough one is struck forcefully by the thought that the grand theatrical tradition of cosy familiarity and showering effusive praise on everybody one has ever worked with – be it 'Mike’; 'Larry’ (that’s Laurence Fox) or 'Ruth’ (that’s Sheen) – is safe in her hands; but struck too by her genuine passion and generosity of spirit. When I tell her that I thought WE was a terrible film ('Oh, that’s a shame…’), but one in which her performance was the single redeeming feature, she quickly disowns the compliment. 'I don’t stand alone in that,’ she says. 'I’m very proud of what we achieved in that film.’

If Madonna’s going down, she’s going down with her…

'She’s not a prima donna in any way whatsoever,’ Marsh says. 'She doesn’t want to be seen as the standout. She’s much more interested in the idea of the film working. A low-budget film like Shadow Dancer is shot very quickly. You can’t mess about and have endless conversations about things; you have to get on with it. And that was a great aspect she brought to it. We were never waiting for her.’

For the past three years Riseborough has been in a relationship with Joe Appel, an American artist, whom she describes as 'my prince’. When she is not working, she divides her time between Los Angeles, where Appel lives, and Boise, Idaho, a part of America she fell in love with after Appel’s parents moved there and she went to visit. 'It’s beautifully epic, and it’s my own slice of privacy.’ She pauses. 'I’m trying to stay away from the term “my own private Idaho”.’

She describes her relationship with Appel as an intensive round of artistic endeavour: playing music, reading, painting. 'Charcoal, pastel, spray paint, pencil, hands, knees, head… anything that can make a stroke or a mark. Anything that we can sculpt or take a photograph of.’

It must be difficult, I suggest, to maintain a relationship when so much of her time is spent away, working.

'One of the things that allows it not to be difficult for us, because we have a wonderful relationship, is really keeping it private – which is why I’m going to stop talking about it.’

She smiles sweetly. She displays a marked wariness about her growing success – the transformation from respected actress to star – and what it might entail. 'I don’t know, Mick. I really don’t know. I’m learning as I go.’

She is trying, she says, to 'stay inside’ what she does and disregard the rest. 'Something instinctively from the beginning has told me that, and it’s served me well. It doesn’t mean that it’s not hard, and that every day it’s not very difficult. But if I thought acting was a breeze, I’d have no interest in doing it. I’m not really interested in doing anything that’s a breeze. Floating down a river on a boat, or having a lovely walk through the park, that’s a breeze.’

Actually she’s wrong about that. Andrea Rise­borough is a wonderful actress. But a walk in the park with her on a stiflingly hot day is anything but a breeze.

We have now circled the lake and come back to where we started. I’ll call the cab, I say. Riseborough says she’ll walk.